In a primetime announcement this evening, President Obama will explain and defend the details of a sweeping executive action designed to keep roughly four million unauthorized immigrants from deportation and provide them with legal status to work.
Some of the particulars remain unclear, but the basic outlines of the plan have been known for months: Obama will use enforcement discretion to redirect law enforcement activities, prioritizing deportation of unauthorized immigrants who have additional criminal records. (You can read the White House’s talking points here.) Republicans have called the move unprecedented and illegal, while the administration, which seems to be prodding Republicans with the move, has argued that it is well within political norms.
As a supporter of expanded immigration and also someone who worries about executive overreach, I think there are partial truths in the arguments made by both sides. And while it seems to me that there are some policy advantages in the executive maneuver, there may also be longer-term political and practical disadvantages to consider as well. 
Obama’s move would probably be legal. For the last several months, conservatives and Republicans have issued increasingly apocalyptic denouncements of the Obama’s proposed action, describing it as a massive legal overreach by the executive. The most compelling comments to this effect, however, came not from the right but from Obama himself, who for years has repeatedly insisted that the sort of enforcement-related order he is expected to announce tonight would be beyond his authority. The White House is now suggesting that Obama has not changed his position, just his emphasis, but as The Wahington Post’s Glenn Kessler lays out in great detail, the record is quite clear: Obama said on multiple occasions that the president did not have the power to unilaterally legalize entire populations of immigrants who are not at risk due to unusual circumstances.
But if the last few years have proven anything it’s that the law isn’t necessarily what Obama says it is. As Reason’s Shikha Dalmia and Case Western Reserve University Law Professor Jonathan Adler have noted, the president has a great deal of authority to set enforcement priorities and exercise discretion when it comes to immigration law. Even some of the loudest critics of Obama’s action have come around to the idea that, at least technically, it would not exceed the president’s discretionary power, even if it would constitute an unusual and strained use of it. 
It would also be unprecedented. The administration and some of its supporters are arguing that various presidents, including Republicans, have taken comparable steps before, limiting deportations through executive order, and that makes this well within political norms. This argument leaves out crucial details about congressional involvement and support for those previous presidential orders. 
In 1987, under President Ronald Reagan, the immigration commissioner announced that children of parents who had been granted amnesty under a 1986 immigration law would be granted protection from deportation. A few years later, President George H.W. Bush granted protection to entire families, a move that followed action in the Senate, and that was passed by the entire Congress the following year. 
Supporters of the president note specifically that Bush, Sr.’s move offered protection to about 40 percent of the nation’s undocumented immigrants at the time, roughly the same percentage as Obama’s move is expected to legalize. But in raw numbers, Obama’s move is expected to have a much bigger impact, granting legal status to about 4 million immigrants instead of the 1.5 million protected under Bush. 
And politically, the actions by Bush, Sr. and Reagan just aren't equal, because both came in the context of clear congressional support for action on immigration. Reagan’s followed a large-scale amnesty law, and Bush’s followed Senate action that would soon become passed by the full Congress.
It would represent a further expansion of executive power, and norms around using it. Just because an executive action is technically legal does not mean that it falls within legal norms, and executive power can be expanded not only through explicit assertions of previously off-limits authority, but by making use of powers that existed but were never used, or never used to such an extent. This strikes me as a case of the latter, especially given the president’s multitude of statements indicating that the power to legalize so many immigrants is beyond his office, and the stated reasoning for his change of heart: that Congress has not acted. When Congress declines to pass a law that the president would like to see passed, that does not give him an excuse to act. As President Obama himself declared in 2011, his job is to “enforce and implement” the laws that Congress makes, not to use his authority to circumvent those laws when he sees fit. Anyone who worries about executive overreach, even those supportive of expanded immigration, ought to be wary of the precedent this move, and the thin line of reasoning behind it, could set.
On a strictly policy basis, Obama’s executive action might be preferable to a big reform bill. If you favor making immigration easier and more straightforward, and think that draconian enforcement efforts are both wasteful and counterproductive, then there are real upsides to executive action when compared to a big congressional overhaul. A major reform bill would massively increase funding for border patrols, despite years of increased funding for border security and little to show for it and the fact that close to half of illegal immigrants came here legally and then overstayed their visas. A comprehensive immigration reform plan would almost certainly include some sort of E-Verify system, an incredibly invasive form of workplace nannying which would create huge hassles for workers and employers, as well as large numbers of false positives—making hiring, and finding employment, an even harder process than it already is.
But unilateral executive action could poison support for broader, more stable reform.There’s no question that the immediate political consequence would be to further outrage Republicans, and turn a party that has long had a mix of views about the virtues of expanding immigration into one dominated by opposition. In fact, this seems to be part of what the administration wants—to provoke Republicans into a frothing rage, in hopes that they will do something politically stupid as a result. (They might oblige.) 
But the backlash might not just be the immediate consequence, and it might not just be limited to the congressional GOP and its core supporters; unilateral action might result in a deepened long-term opposition to greater immigration as well. 
One only need to look at the political dynamic in the years since the passage of Obamacare, another ambitious policy passed with no opposition party support and a wary public. Democrats hoped it would provide a path to political victory, but the actual result was a deep and enduring public opposition that has cost Democrats in multiple elections.
Similar to Obamacare, about 48 percent of the public disapproves of Obama’s proposed action, while just 38 percent say they support the move. And similar to Obamacare, the president's actions are making some Democrats nervous too. And just as before, supporters are arguing that opposition will blow over quickly. 
I wouldn't bet on it. Unprecedented, unpopular, large-scale, unilateral policy changes are nearly certain to produce a backlash—against the president, against his party, and against the ideas at the heart of the policy change itself.
To me, this is the most significant risk of Obama’s plan—that it will create a backlash, not only amongst congressional Republicans, but within the public at large, a backlash that makes it more difficult to achieve a stable, legal, and politically viable system of expanded and simplified immigration, one that is not dependent on a sympathetic executive or enforcement discretion, but that is codified in law and agreed upon by enough of the country’s residents and legislators.
This is not to simply condemn Obama’s plan, but instead to warn enthusiastic supporters that the choice to act at this time, in this way, without legislative backing or public support, might be satisfying in the moment, but also stands a real chance of closing off opportunities for a better, more lasting solution at some point in the future. Consensus is hard, and sometimes it seems impossible, but in politics, it’s also important.